Fluorescent lighting systems



Dec. 20, 1960 J. F. ROESEL, JR., ETAL 2,965,804

FLUORESCENT LIGHTING SYSTEMS Filed May 5. 1959 Fig. 3.

WITNESSES INVENTORS John F. Roesel Jr a Thomas M. Cor r y. Wzefl W ATTORNEY FLUORESCENT LIGHTING SYSTEMS John F. Roesel, In, Pittsburgh, and Thomas'M. Corry, Monroeville, Pa., assignors to Westinghouse Electric- Corporation, East Pittsburgh, Pa.,- a corporation of Pennsylvania 7 Filed May 5, 1959, Set. No. 811,049.

2 Claims. or; 315-201 This invention relates to electrical supply'circuits for electric discharge devices of the type employingioniza-v ble mediums such as gases or'vapors, and more particu': larly to high frequency circuits for fluorescent lamps. j

Circuits now commonly used with fluorescent "lamps are designed to operate at an alternating'current frequency of 60 cycles per second" or less. Control circuits for fluorescent lamps operating at this frequency general- 1y require component parts such as transformers; re actors and capacitors which areh'eavy, bulky and 'relatively inefficient. If higher frequencies are used to en: ergize fluorescent lamps, the components can be designed so that they are smaller in size, lighterin weight, and have lower watt losses; thereby generally achieving lower production costs. Anobje'ct of our invention, therefore, is to provide new and improvedfelectrical operating "circuits for gaseous discharge devices. i f

A further object of our invention is to provideatlighF ing'system in which the source-of the liiglifrequency current is located adjacent'to the lamps or luminaries which are to be supplied. V I

Still another object of ourinvention is to provide" a new and improved starting and operating circuit for fluorescent lamps suitable for lightweight luminaires.

Still a further object of our invention is to provide a new and improved starting and operating circuit for fluorescent lamps operating at frequencies substantially above 60 cycles per second.

These and other objects of this invention will :become more apparent upon consideration of the following detailed description of preferred embodiments thereof, when taken in connection with the attached drawings, in which:

Figure 1 shows, in block diagram form, a lamp or luminaire having an independent high frequency source operating from a low frequency or direct current line;

Fig. 2 shows, in block diagram form, a system for operating several lamps or luminaries from an adjacent centrally located single high frequency source; and

Fig. 3 shows, in block diagram form, several banks of lamps or luminaires, each bank having its high frequency source, with the individual high frequency sources operating from one alternating current to direct current converter.

In general, it has been the prior practice to supply gaseous discharge lamps of the fluorescent type from the ordinary 60 cycle source in common usage. Ballast components, whether inductance, reactance or resistance, have, of necessity, been increased in size and weight when using this relatively low frequency source of supply to start and operate the increasingly higher wattage gaseous discharge lamps which are presently used to produce more lumens. However, if a high frequency source is used as a power supply, it is possible to reduce the physical size of the ballast required, while substantially increasing the lamp efficiency. Since it is desirable to have electrical components and fixtures which will not require a different gaseous discharge lamp than that ice which is commonly used, the impedanceof the electrical lightingv system. should remain relatively the sa'rn e. Therefore, if the; inductive or'capacitive reactance of "the lighting system is to remain the same, but a much higher frequency source isused, theinductance or capacitance needed to start and operate a gaseous discharge device can be reduced in size with a corresponding reduction'in weight. If a frequency having a range of 1500 to-4000 cycles per-second is used, it will readily beseen that the inductive or capacitive 'reactance willbe greatly reduced;

Ifithe'weight of theballast or' ballasts incorporatedin alightingsystemican be reduced, it would then bexpos sible to mount closely adjacent the ballast several other lightweight components such as an alternating current to direct current converter and a static transistorized high:frequency inverter within theconfines of the Iuminaire-without substantially increasingithe weight of the luminaire or reducing its utility.

Referring now to Fig. 1 of the drawings, an input power line 10, operating at a'frequency ofapproximately 60 cycles per second, supplies a luminaire fixture 12 (shown'in dotted lines) with its'leads' connected to'a small alternating current to direct'current converter .14. The converter 14 can be of any knownstatictype incorporatingdiodes. Thealternating current to directcurfrent converter'14 generally has a relatively. small come pact size and is lightweight such. that item readilybe mounted within a luminaire fixture; Electrical. cons ductor 16 can then be 'used'to conduct thedirect'current to a'static transistorized high frequency inverter 18. An example-of an inverter that canbe used is'disclosedinra lcopending application, Serial No. 726,934 .of ,Johnj F.

Roe'sel, Jr., entitled Electricalrlnverter Circuits; filed April 7, 1958 andassigned totheypresentassignee. ,By electrical conductor 20,1: ballast 22, :whichds disclosed in copending application, Serial No. 834,306 of John Roesel,'Jr. and Alfred E. Relation, entitled High Frequency Fluorescent Lighting System, filed August 17, 1959 and assigned to.-the present assignee, is supplied with high frequency alternating current. The. static transistorized highfrequency. inverter .18f,.as previously disclosed .in: thereferenced application, is of a size and.

weight thatalso may be readily mounted within thelumi-i naire fixture so as to present a' plea'sing'configuration. The ballast 22 is electrically connected to the static transistorized high frequency inverter 18 by means of an electrical conductor 20. I

Electrical conductors 24 and 26 then connect a lamp or lamps 28 in series. Common practice requires that only two lamps can be connected to one ballast. If the luminaire 12 is to have four lamps, the static transistorized high frequency inverter 18 may be used to,supply one or more ballasts 22 to compensate for the additional lamps in the lighting system. As shown in Fig. 1, each luminaire has an independent static transistorized high frequency source operating from a low frequency or direct current line. By incorporating a static transistorized high frequency inverter in the luminaire 12, the luminaire 12 does not require any high frequency electrical conductors to be located outside of the luminaire fixture, which reduces the energy lossesvof the electrical conductors.

Fig. 2 illustrates the proposed system for operating several luminaires or clusters of lamps each cluster comprising one or two lamps from a single high frequency source. The alternating current to direct current con verter 30 is supplied by an input power line 10 and has an electrical conductor 16 for the output to supply a high frequency inverter 32. The converter 30 and the high frequency inverter 32, in this particular arrangement, can be mounted outside the lamps 28 and ballasts 22, such as, for example, where the high frequency inverter Patented Dec, 20, 19 6Q 3. 32 is to supply a large number of lamps for one floor of an office building. In connecting a number of lamps 28, it would be best to have a relatively short electrical conductor 20 supplying the ballasts 22 from the statichighfrequency inverter 32. In this manner there would be'less line losses. than if one central high' frequency inverter 32 were used to supply'the entire olfice building of several floors hecausethe high frequency. inverter 32 is. located. closer tothe; lamps 28. Consequently, this particular lighting system would have the advantage of maximum utilization of inverter and rectifier capacity.

Fig. 3 illustrates a lighting system where a large amount of electrical power is required, but a number of high frequency inverters 38 are located close to lamps 28 so as to keep thele'ngth of the electrical conductors to a minimum. An input power line is again used to supply a large alternating current to direct current converter 34. Electrical conductors, 36. conducting the direct current output of the alternating current to direct current converter 34, supply the static; transistorized high frequency inverters 38. The high frequency power source conductors then supply high frequency power to ballasts 22 of the lamps 28, thereby keeping the high frequency supply lines 20 at a minimum length. The particular system embodied in Fig. 3, as can readily be seen, can be used to supply high frequency power to banks of lamps located on different floors so that, by way of example, an alternating current to direct current converter can be centrally located in a large building, a high frequency inverter can then be located on each floor and centrally located with. respect to the lamps, thereby minimizing the length of the electrical conductors 20. Furthermore, by using several high frequency inverters 38, maximum utilization of the rectifier systems is provided. It is to be understood that this invention is not to be limited to the particular embodiments of the lighting systems specifically described herein, as it will be readily apparent to persons skilled in the art that various changes and modifications may be made in this particular lighting system without departing from the broad spirit and scope of this invention. Thus, the lighting system may incorporate several alternating current to direct current converters, or a great number of high frequency converters supplied by several alternating current to direct current converters, or if direct current input power is available, the alternating current to direct current converter can be eliminated. The embodiments shown are merely illustrative and are not to be taken as limiting as to the forms which this invention may take and of other ways in which the invention could be used. Accordingly, it is desired that the invention be given a broad scope, and that it be limited only as required by the prior art. 7 s

We claim as our invention:

1. In asystem for operating fluorescent illuminating means, a source of relatively low frequency alternating electric current, converter means electrically coupled to said source for changing the alternating current to direct current, a plurality of high frequency inverters coupled to said converter for converting the direct current to relatively high frequencyalternating current, said high frequency inverters being remotely located from said converter, ballast means and illuminating means electrically couped to each inverter, said ballast means and said illuminating means being located adjacent the correspond: ing high frequency inverter, each of said high frequency inverters thereby supplyinga limited number of ballast and illuminating meansto reduce high frequency conductor losses.

2. In a system for operating fluorescent illuminating means, a source of relatively low frequency alternating current, converter means for changing alternating current to direct current, circuit means for coupling said source. to said converter means, a plurality of high frequency inverters for converting direct current to relatively high frequency alternating current, a number of first electric, conductors for coupling said converter means to said inverters, a number of ballast means and illuminating means, a number of second electric conductors for coupling at least one of said ballast means and illuminating means to respective ones of said inverters, said second electric conductors being relatively short with respect to the length of said first electric conductors so that each of said inverters supplies only adjacent ones of said hallast means andilluminating means and so that said high frequency current travels a relatively short distance so as to reduce high frequency conductor losses.

References Cited in the file of this patent UNITED STATES PATENTS Chinskey Aug. 30, 1938 

